Breast Cancer Subtypes

Breast Cancer Subtypes Based on Histology

Breast cancer is an abnormal growth of cells within the breast. Most commonly it arises from the cells lining the milk ducts (ductal cancer) or milk producing lobules (lobular cancer). However, it can arise from any cells within the breast.  

If the cancer cells stay within the duct/lobular system it is called in situ cancer; either ductal carcinoma in situ (DCIS) or lobular carcinoma in situ or (LCIS). If the cancer cells pass through the duct/lobular system into the surrounding breast tissue, it is called invasive breast cancer (invasive ductal or invasive lobular carcinoma).  

Breast Cancer Subtypes Based on Receptor Status

A more contemporary and useful way of discussing breast cancer subtypes is using the receptor status on the pathologic analysis. Breast cancer cells may or may not express estrogen and/or progesterone (so called hormone positive or negative). The other receptor is called Her2 which if overexpressed can be responsible for rapid growth of cancer cells.   Based on these three receptors, breast cancer can be divided into the following 4 subtypes:

•  Hormone receptor + / Her2 - 

•  Hormone receptor + / Her2 + 

•  Hormone receptor - / Her2 + 

•  Triple negative (Estrogen, progesterone, and Her2 negative)

The importance of this classification is its implication in the treatment of breast cancer. For example, a patient with hormone positive breast cancer will benefit from anti-hormone therapy. Similarly, a patient with Her2 + breast cancer will benefit from specific anti-Her2 medications which is administered along with chemotherapy. On the other hand, patients with triple negative breast  cancer most often will need chemotherapy as none of the other systemic therapies are going to be effective.